Float value less than 0.0001 (0.0000999999999999995) will be converted by floatval to scientific notation (exponential notation):
<?php
var_dump(floatval(0.0000999999999999995)); # >> float(0,0001)
var_dump(floatval("0.000099")); # >> float(9.9E-5)
var_dump((string)floatval(0.000099)); # >> string(6) "9.9E-5"